keith



H. L. KEITH.

MOTOR CONTROL SYSTEM.

APPLICATION FILED DEC-H.1918.

1;400, 77 Patented Dem-13, 1921.

ifHEETS-SIIEET I.

INVENTOR Hard/d L. h eff/1 WITNESSES:

IKJMLMMHW BY MW MW H. L. KEITH.

MOTOR CONTROL SYSTEM.

APPLICATION FILED DEC. I4. 1918.

1,400,077, Patented Dec. 13, 1921.

2 SHEETSSHEET 2.

INVENTOR WITNESSES:

M754 1% z m Ham/d L Ire/7h BY my UNITED STATEjfi.

RAT-ENT- .QFFICE;

mm m smnou 1'0, .wnemqnooes ELECTEIQ a: muimccmnnm comm. .econiomxon 0R reuiemvm moron-oomnon s sm;

n uqauomme Decanter- 14.- 1am. Mo Ear- 28mm.

.o. new-(and ns'efuLlm rovmenfilinollobrn Controlfiyotems, of :w on the followingnim a specification;

My .1; inventionwreiams 1o.Imournscontour, systemsi.and,.particu1a1:ly;tn58uoh"8ywms-es; embody means'ior .antomaticallynaocelrahf; ing. c1ectrio=motorsandiior ath': same to rest 'by-emeainsedf dy'nnmie; u

vide '9. simple armxigemdnlmiher'ehfii iii! 60%) trio motormaiy. be mtbmafimlHY-andi dill.

all-y accelerated {UPON-111B! hlodngiofiil dih:

cuil; imd wherebyeaid motor. mnyl 1381131200 ht:

wrest. quickly, and. =salf ely .-byemmns=o ya: graduated .dynomio-bmki ngfiorce.

MY invenbion is nparhoqlhrljl applicable; to 'e evaj ors hoistsmndluhilnfi lfldch'mhfle Iprovide the motorlbfisuch evmadliinmwith; three resistors one of whichi'fi' inflieries with themotor annoturetand .the-mtheiruflfo 111';- shuub' therewith The sexier.resistor; niayvber short circuitedrlto :fl'eohhthm-M WmQQMymw colorationof the; :inotoqipno; ofigthaiohunt! resistors may-.be: E eniployfi gin conjunction-4 with :lhegseriea-mesistor, m sieoelerawgdie motor -nudthernt'her shuntsre'flis qr; besides; aidin the decelrutin g goperfition so -c bn-; "m5 as,to pre'vente pnemuihire reversal of.

, the motor.

'tlu'ough a relay.

In the accompanyingdrawings, Figure 1 is a diagrammatic view of circuits and apparatus embodying my invention. Fig. 2 is r. diagrammatic view of a schematic arrange inc-mt of the system of Fig. 1. Figs. 8 to 7,

-variousf =f-oirchifsi-"combleted throuzh' the ezconauotors l' andifi gwhich ins. lie P WP yae bl ir am em, supply powen 0'0 an mofiir eo haying an arlnntnre 3 undo shunt lim '.-I [lie notor b'e ope: etmely 'o'mmeo d;i tfoz j'e;e.i nole; -an 'eI6-. vatofircoro -The direction of rotation ofthe z notor-r-lsaw'ntrolied '-hy mv1sing oontigtors' 85 a, 6-, 7: anti 8;"the'=oontdoto1 sj{ fiend "7 and; 6' enable bmgErmwbIvQIw'mQchmiCmWebn nected :iriipnirsfl $1 4 s'eolzzonhllastartingwjstorili whi'oh some mambo-timot y: egfis conmllefi by wo a; semekmf pmgressweig actuated 1.132112125135714, 31 5 .16: fifleiktorjl'l, vrhiciras 'ada zlted tmbe connected in parallelmthrthmarinatprelii, is controlled-bi a'oezi of contac tore 18, -19 a.nd 20. A resistor-"223 whichusgn iezrcgitswithathe shunt field-'magnet-'wm yis -controllecl'hy rela'ys23 aii'd 24. iThanresistobflfI is adopted :00 ben nete' an-afriynzimicbi aking'circuitf A one} dynamrcsabra'king circuitoomprises' w resistor 25flwhiohqis=oonnedted mar cii'ouitewvitlmgthx-smotor armetmfi 3 switches 26 and 27 that are respectively com necbedrtozthe ro'i'ergingmntactors (rend 6:-

-fl3he;-oircuitm of the aotuatin coils of the scrotal contactors ere gowerne' by a master sw1tch-28:-xghicli comprisesm sene's ohm? tionary contentsmembers =29- nnd'30 and. a. movable" '-c5nta'c't-.- seg'nient 31; which .5 -s1 1ocessively the contact members 29 or '90 mymcoording? to: the direction in which the: masterlgswiteh handle is actuated from its o'fi orbinoperativeposition. The system com f gency sfvitch 33 and 133 is also closed, a circuit is completedwhich eitends from the positive line conductor 1, through the 8.7:, by condoctors 101, 201 and 301, through the actu- -9. 1-; 3.- Of emeinrline contector 39; a ooggfuctor. 4:0, the. pilot switch L33,- condoctors 42 and 43 and the switch 37, to the.

negative line. conductor 2-. The main-line contsctoy: 39-

then close and willremain closed so long as the pilot switch 133. is o ed- The arm of the master switch 28 may, in practice, be actuated quickly to either ofthe ertreme. limits of its eth oi movement, or it, o erated: owly. If: the master. switch arm actuated uickly,themotor willaut m i il l-lo'. be erated to its highest spee if compara'tivel slowly, the operration will depend; upon, the ositlon; oi the controller. arm, but the no t will: be sub? stgntielly the sumo. The master: switch arm may be, actuated very slowly, in which case, as, described below, the motor, mcy. he brought to any one ofi several predetermined 5 L shall f rst describe the operation 05 the motor, assuming that the master switch urm hesbeen actuated: to an extreme limit of its path of movement quickly, but I shell describe the operation in the sequence produced by the step-by-step actuation of the master switch to.its several operative posi tions.

Assuming, for. exam ie, that the master. switch arm is actua in a oountec-clockse direction to cause the movable contact segment 31 to successivel Bridge the'stm tionary contact members a. circuit is, completed in the first position. of: thecontroller, which extends from the negative; line conductor 2; through the switch 37-h the conductors 43 42' and 44, and through the switch 136, to the contact sement 81. This segment is thus. permanently connected to the line conductor. 2 but the circuit may be broken at the switch 136, in accordance with the operation of the governor 36.

From the, contact segment 81, the circuit continues through the first two contact mem bers 30, which are bridged by the contact cut 31, the conductor 45, the limit switch 34, the actuating coil 40' of the reversing switches 5 and 7', a conductor 46, the safety-plank switch 233, the emergency switch 33, the limit switches 35 and 34, con- (luctors 47, 201 and 101, and the switch 37,

to the positive line conductor 1.

The coil 40' is energized to close the r the coil; to for con he switch 27, conductors 165,265 andt3 5, the brake coil 53, a conductor 153, the contector39, the

conductor: 48, and the switch 37, to the line conductor"v 21; ahd: from the conductor 165,

which, as may be seen, by reference to the circuit just traced, is connected to the conductor I, through a. conductor 485, the coil 54, the contactor 39, the conductor 48 and the switch. 37-, to the line conductor 2. Simultaneously. the closing ofi the motor circuit, therefore, the brake is-released and the neley M is -clqsod: toshort circuit the resister and: thus to insure a strong magnetic fieldxin. stoning the motor. Themsm motor circuits, as they appear. at this time, are diagrammeticellyshown etFig. 3. The circuit of the Belchm I et 4 exteh (is from theili'ne eonfictor-l, through the switcl'i'3 7," the'fie'ld-m et w-in Qthe resistor: 22- and: the sw tch 37, to conductor 2, When the role. 24 isclosed, the circuit extends from the e conductor 1, through the switch 37, the field-magnet winding-=4 a 'conductor 122 the relay 24, the line contoctor 89, the conductor 43 and the switch-35 theliueconductoc 2.

e winding tund; the brake coil 53 are in pmctioe shuntedby resistors, which ere diagrammatically illustrated at Fig. 2 but which, along with other refinements, ave been omitted from Fig. 1 in order not to complicate the circuits of that figure unnecessaril When e msster switch arm is actuated tothe second position, a circuit is completed from the contact s out 31, which is connected to the mega fve line conductor 2, through the third contact member 30, a. conductgm 10, the actuating coil of a contuctor 1L0, the resistor 25, the actuating coil of the relay 23, the coil 65, the switch 27, the reversin contector 7, the conductor 101 and the switch 37 to the line conductor 1.

As the actuating coil of the relay 23 is a series coil, it is not sufliciently energized to effect the closing of the relay 23. The actuating coil of-the contactor 110, however. closes that,- c ontector to cause the opening of c switch 2l0 which controls the actuating coll 1520 of the contactor 20.

When the muster-switch arm is actuated line to its third position, .a-cirduit isnompleted from, tim contact .rsegment 31; which-iacom necbeii to I thenegatiize line :oonductor: 2, through the 'fourtkcontactmmmber 30; P a conductor 21., ,thrlou h the actuating-abilof a cont-actor, 121mm the confiacbmr 110,, b

the conductnrs 301, 201 andlfli, and througii the swiwii 37,, Lathe line onduciionl. Enerizati0n of this eircuit causes tha losing of t m contac'tan 121.,am1 the con unnhopeflingofa switch 221, whichpontro' the act auug coil 1190M tha-,contacto'r-..l-9. Tha function, of; the actuating coils J30 411M119 apd the manner 02 their cqgtrol by the switches 219 11nd- ,221 is described below.

Whentha master-switch arm is actuated to its fourth .ition, a airpuit i s complehed which axten from the-gmovuble Contact segment 31, which is connected to the magi tive iine conductqr 2, through tha fifth contact sagmentJBO; by a. conductor 55 th r ough the aetuatingxoil oithe eontactot 11" and the switch 3. 1 aniby the. wuductorsBOl, 2013116. 101, to the awitchBTandtha positive, Jim; condugten l.

The contact/or lbisjihqn galqaed,, bo short circuit a saction offha resktogh-asshown by full lines ai; Fig; 4, I1d,-)E lel. the current traiyegsing the amber cixcuip fa lls g pref dete rminqd w lue ga relay; 55,8, qfln H 1s1 npw gal y e mz w q mi tq 1, ,d m to cgi-mglctb 2 mil-cult; I01, thg ,aqtuz gngwoilof thacontaclgori, ThO ,QIQS iLIEIg 10f the qqntacmr 11, iuijhh egmom opgigajzgytg e why 59 hhat is meclihpiqgljy p9pnepedhpreq to o n the circuitnfiighaagtuhiiinggoil 118 tt =9 'th s, s2 .qi1 .i mam l ed being w w l' x 9 -2Wa9 3 si hiya ,fgorce pf the. meta .foipws .fgoxii the point 1 h h wqw. J2 m" iilm. MW W. isfiia w ii; mwi l'l .11; relay u 'fii sw idi awz t9. 10 whifzh is cpnxiected to the oflwz, r ii Hammih M m se o 1 11 t Q; S }Y: 591M, this tim zrfbggqya, $62130b512$9d haLxbeconge great agonghgto gieyuio suifiicpfi. cnuntgrlelectronmtivajcrca to ,0 use the; cpntaqtdnlB through the ener izzitiqn (if the. ,zibove-trabgd. cii'quit of the} 0011 118, is, to pxgj gnt the; 0108 big qf'the contzictpr ll 8zahd thpsiopmchido the insertion into the, motor nincuit of fihi rvsistm- 17. Thenormal accelerafion of the motor is thus. gfi'ectd 'mzihs of the re sistor 9 519110, and tli nei'gy which woi ld be dissipated current which would qthcv wise tmversa tile resistm- 1'1. is s-iivecL The opening of the switches 21D az d 22l iippn Lhe cont-roller am] reaching its second and third positions, respectively has a similar purpose in view, muneix that 0fpravenhiug L110 encrgizution of the coils Y320 and 129 dun ill the normal acceiaratiun of Hm motu': 'rliicii it is :inszii'ud 0 itffsct With-val, c-zupEuy ing the rwsistnr 17, This will m. belt-,1 untyoilizgg diitstood from the description given below. The necessity for closing the coutactors 110 and lQL'bBiQIB the operation 01 shortcir uniting tlia .i-esiktor 9 has commenced, furthermor iyrovides a time-alumni: for com e shortwmmuiting operation of the resistorik which is foimd,.m practice; to be very beneficmii The .ciJcuit-ni the actuating coil of the conimsiwmifimay b'e: tracd iron) the posi tiy Kim: conductor], through the svvitch'S'Y, thii ,engiiucfm' 101, .the reversing :switch 1", time sw tchg f, the" coil 65, the conductors 165 :mdflfifi, thwactuating coil of the contactor lzgthareiay 58,1;hfl conductorsbi; 42 and 43 and 'the switch 37, to the negative line conducto'x 2. nUpon the; closing 01' this cir- Cuit,th:9:flllill0t0ff 12 is closed to shunt a sacundection of the resistor 9. A relay similzw to. the relay 58, which is mechanicall oonnabbed to the contactor 12, closes to nompiete a :circuit fill the actuating coil of the contaqtor 13', this yell being in pan ailel relation tmthg actuating coil of the contactpr, l2, Similazly contactors 14, 15 and lfi gcl osa uutqmgticnily when the current trQv01s ing ;hgjwj1 of the current-limit relqy ti atus' eglgmcted to the preceding contaqtoz, igqpipgeg; falls m4 2L, predetermined val eg jligc gnqcgssiw stepsl are diagram mgtgcgl} mskagadfiit F3 The. gradual dqcxw jgpreaigtancgnf eserias ircuit o @11 {11015113 causes tha gg'adnal acceleration of thermqbqp i ffliggigggfinqtQrgll, gontrols agsgotion of the' reygwgflg, ggbigh jf the 10601; wgrmoperap ,g- -:l iiglqa xsm yb i 1 b d pm in EXQWQQILP t i n M1 9 1 92k. a .i qw v B fu P pg 1; dyigz; i qyqqelez gyiogi of the motor, 111; q

ih mgpl} an iwmontrolled by Mai- .39mi) g goided. 1Q:c x xhaavy w rgg thq iqotgn-qvip nqhjark; sq g.;t,.i; a par n oi fiip xes swr whichJs. cqntxiqlleaz By the, mzitgqto: 11-, could be 0125i; 2 igiithe motdr were n.dapod for heavy 1036; 9x51 'Whan f, g: -xiigistdrswi tch arm igs actuated t0 thq fiflgh .igi'finul position, a slmrt. circuit is esfniflishpd which cxtgnds.irom the lin cdnduqip 2,1;hmljgh thwswitcb. 37, the conductor 13', 1.3m ling: 39, theic oil 54, the conduc 01," 46 through th switch 62 which, lining melmnically conneitt'ed tot-he last ucceierat .1

511g cpntac'iol; 16,33 clos'ud whail that switch ls c1osed, an l the conductor. 162, to the last :ontact mem'iier 30 which, in the final posi- Lion 0"! the mnstr-switch arm, is bridged by the contact member 31, w bich is comiecbed to the jifi 'flijYfi linll cundnctcr 2. The. short oil-suiting of the boii 54 permit; the opening of the. switch-9A to insert the resistor 22 in series with tlie shlint fiekimugnnt winding 3., as is diagrammatically indicated at, Fig. '5,

jig ig iggt suddanji rks. of the thereby further to acelerate the motor. The motor then operates at-its normal speed, with the entire series resistor 9 short-circuited and with a weakened magnetic field.

If, during the acceleration of the motor, or, after it has been brought up to speed, the motor speed exceeds a predetermined value, the switch 236 will close to cause the closing of the circuit of the actuating coil of the relay 111. This circuit extends from the conductor 165 which, as may be seen by reference to the circuits traced above, is connected to the positive line conductor 1, through the actuatin coil oi the relay-111, the switch.236, con uctors 4 4, 42 and 13, which is connected to the negative line conductor 2. The closing of the relay 111 causes the closing of a switch 211, which is mechanically connected thereto, to create a holding circuit for the actuating coil of the relay 111. This holding circuit extends from the conductor 165, which is connected to the line conductor 1, through the actuating coil of=the relay 111, the switch 211, the conductors 44 and 42, which are connected to theline conductor 2. The closing ofthe relay 111: causes the short-circuitingof a portion of, the resistor 22 with the consequent strengthening of the'mo'tor field and corresponding reduction of speed, thecircuit bein fromflthe line'conductor-1 ,=throu(gh the switch 37, the shuntfield-magnet win ing- 4, a portion of the resistor'22, the relay 111,- the conductor 43 and the switch,37 to. the

line-conductor-2. The creation. ofa holding circuit for the coil of the relay-111 prevents the continued 'opem'n and closing of the relay 111 which woul otherwise be caused" by the continued 0' ening andclosirig dlfthe switch 236 in accor' ance with changes; "in the 7 speed of thetmotor; Should the motor fail to respond to the operation of the rela 111 when closed and attain a second and hi" her predetermined speed, the switch 136 wi be opened to cause the opening of all thecontrol circuits, and stop the 'car. The. relay 111, once closed, cannot be reopened until the master switch handle isreturned to, its off position or until the switch 136 is opened, the latter, of which will be caused by excessive, undesirable speed ofthe motor.

This arrangement of circuits. for the relay 111 permits regulation of themotor within predetermined limits, say 15%, under all load conditions. If the elevator car, for example, starts downward, heavily loaded, it may overspeed, in which event the relay 111 will close to effect automatically a desirable speed reduction. After the car has been stopped, at any desired floor, by suitable manipulation, to the 011' position of the master switch 28, and, a number of passengers having alighted, restarted downward with suliiciently reduced load, the relay 111 will remain open because there will be no overspeed-ing. The change in load afiects the motor speed, and the relay 111 remains open or becomes-closed in accordance with the speed of the governor 36 which is controlled by the speed of the motor. Once closed, because of excessive speed, it remains closed'vuntil reopened by the master switch to suit a probably changed load.

The switch- 136- is so designed (although this is not; illustrated, it being common practice)v that, once it has been automatically opened by excessive motor speed, it cannot be again-closed except manually.

When the-master-switch arm is operated toward the off position, the shunt circuit for the coil 54 is opened in the fourth positi'onof the controller and the'switch' 21' closes to shunt the field resistor 22 and, therefore,-strengthen the magnetic'field of the motor. The circuits are-again as shown at F ig, 4, the risistor 9 still beingshort-circuited. The motor speed is reduced. The actuation of the master-switch arm to its third position opens the circuit of the actu atin coil of the contactor 11, and the latter, in opening, causes the opening ofjthe relay 58, which breaks the circuit ofthe actuating coil of the. contactor 12; Similarly, the opening of the contactor- 12 causes the opening fthe-relay which is mechanically connected thereto to cause the openingof'-' the circuit oftheactuatin coilof the contactor13', In similarfas ion,the contactors"14, 15;and*1-6are also opened, each con tactorf, as it? opens, inserting a; corresponcl-' ing sectionfof the resistor -9 into the motorcircuit,';as',i's illustrated at Fig The opening of thebontactor 11 permits the closing of'the relay 59 which, thereupon, closes thecircuit, above traced, of the coil 118 across'the terminals of the motor armature. The contactor 18"is thereupon closed to connect the resistor 17 in a dynamicbraking circuit across the terminals of the armature, as is illustrated'by full lines at'Fig. 6. The circuit extends fromthe point 105, Which is connected to one brush of'the motor armature, through the resistor 17, the actuating coil of a relay 218, which is mechanically connected to the contactor 18, and the. contactor 18 to the point 104, which is connected to the other brush of the armature 3. Energization of this circuit causes also the energization of the actuating coil of the relay 218, which relay will remain open until the current traversing this cir cuit falls tov a predetermined value.

When the master-switch arm is actuated to its second position, the circuit of the ac tuating coil of the contactor 121 is broken, wherciipon the contactor 121 is opened and the switch 221 closed. When, therefore, the relay 218 is closed, in accordance with current conditions, a circuit will he established for the coil 119 of the contactor 19, extend closed to cause the-short-circuit' ing from the positive line conductor 1 through the switch 37, the contact members of the relay 218, the coil 119, the switch 221, the contactor 39, the conductor 43 and the switch 37, to the negative line conductor 2-. The closing of the contactor 19 causes the short eircuiting of a portion of the resistor 17, as indicated by the dotted line 19 in Fig. 6.

The dynamic braking circuit may now be traced from the point 105, which is connected .to one terminal 'of the armature, through a portion of the resistor 17, the actuating coil of a relay 219, which is me chanically connected tot-he contactor 19, and the contactor 19, to the point 104, which is connected to the other terminal of the armature 3. Similarly, if the master-switch arm has been actuated to its first position, to break the circuit of the actuatm' coil of the contact/or 110, the switch 210 will closed and, when the relay'219 has been closed, in accordance with current eondi tions, the circuit of the coil'-120 will be of a secend portion of the resistor 17, in 'cated by the dotted line 20 at 6. The coil 120 is inparallel relation to the coil 119. Finally, when the oounter-electromotive force of. the motor falls to-a sufficiently low value. the coil 118 will become deenergized and the contactor 18 will open (this usually taking place after the motor is atrest and the magnet brake applied), causing the opening of the relay 218 which, in turn, will cause the opening of the circuit of the coil 119. The contactor 19 thus opening the relay 219, will open to open the circuit of the coil 120. The resistor 17 is now disconnected from the motor circuit, as is diagrammatically represented at Fig. 3.

It will be obvious that the coil 118, like those numbered 1.19 and 120, may be connected directly across the line, instead of bein energized by the counter-electromet-ire force of the motor. In either event, the relays 218 and 219 for controlling the coil 119 and 120, respectively, cannot be closed until the current in the dynamic brakin circuit, including the resistor 17, falls to a suflicicntly low value. I regard this current limit slow-down as a. very important feature of my invention. If the coil 118 is connected across the line, however. this coil may be energized before its circuit is bmlren at 59, in which case, the alternative accelerating operation described below, with the aid of the resistor 17, would obtain.

It will be noted further, that, according to my system of control, the series resistor 9 is first entirely inserted into circuit and then the resistor 17 is operated to control the deceleration of the motor. I consider this system to be an improvementupon the systems of the prior art which control both resistors simultaneously.

The insertion of the series resistor 9 and the gradual shunting of the parallel-con nected resistor, 17 operate to quickly and smoothly decrease the speed of the motor by reason of the increased resistance of the armature circuit and the establishment of a low-resistance shunt circuit or dynamic braking circuit for the motor. In practice, the master switch handle will be held in this first position until the motor has been retarded to a speed from which an accurate stop is readily accomplished by further dynamic braking combined with the magnet brake.

'When the master-switcharm has been actuated to its oil or'illustrated position, braking the circuit of the coil 40', the reversin contactors 5 and 7 will be opened to open tie armature circuit of the motor and the switch 26 closed. "The circuit of the brake coil 53 is opened by the contactor 7, allowing the brake to set, the deenergizing of this coil beingdelayed by the shunt circuit, shown at Fig. 2, comprising-a discharge resistance which connects its terminals. An additional dynamic brakin circuit is then established from one 'brus f'of the motor armature, through'the switch 27, the coil 65, the actuating coil of the rela 23, the dynamic brake resistor 25, the coil 66 and the {switch 26, to the'other terminal of the motor armature 3. The circuits are diagrammatically illustrated at Fig. 7, a temporary parallel path being shown also through the resistor 17, either through all of this resistor or through part, depending on how quickly the master switch is returned to the 01f position. This will be better understood in connection with the fuller description of the operation of the resistor 17, which is given below. An additional dynamic brake circuit is thus established to aid in slowing down the motor, and, since it comprises the coils 65 and 66, the motor cannot be again started, either in the forward or in the reverse direction, until it has come nearl to rest, the coil 66 overpowering the coil 40' to prevent the closing of' the reversing contactors 5 and 7, and the coil 65 overpowering the actuating coil of the reversing contactors 6 and 8. The contactors 5 and 7 and 6 and 8 may be mechanically, as well as electrically, interlocked. The motor is then brought quickly and safely to rest.

The relay 23 closes to short-circuit the resistor 22 so as to provide a strong shunt field for the motor'during the dynamic braking period. The circuit of the shunt fieldmagnet winding 4 extends from the positive line conductor 1, through the switch 37, the field-magnet winding 4:, the conductor 122, the relay 23, the contactor 39, the conductor 43 and the switch 37 to the negative line conductor 2. l? hen current ceases to traverse the dynamic-braking circuit, the coil of the relay 2 3 clecnergized and the latter opens :to. insert the resistor 22 into circuit withfthcwinding 4. Thefcircuits arethen ready for the nextsuccceding operation.

According to my invention, three resistors are employed, one of which, 9, in series with the motor armature, serves to control the motor during acceleration and deceleration, a second, 17, inshunt withgthe motor armature, controls the. deceleration of the motor, and the third, 25, inshunttwith the motor armature, controls the deceleration of .t 11e motor and prevents premature reversal; The resistor 17, may, however, be also 'employed during acceleration of the .motor to control the; motor speed.

, In order to avoid the necessity for describthe .reverseoperation of-tl e motor, the speedscontrol operation, by meansgot tlige resistor {17, will now,be,described nponthe supposition that the coiitact segment 31 makes, contact with the contact members29. It will beundcrstood, 'however, that,,whe re I have described the operation upon the-supposition t-hat the contact segment 31 bridges the contactmembers 30, a c orrespondjngoperation exists, with correspondingly changed circuits, for .the contactmembers 29, and, whereI shall hereafter describe ;the operation upon the supposition that the-contact segment 31 bridges the contact members 29, a corresponding operation; with correspondingly changed circuits, exist when the contact segmentfil bridges the contact mern hers 30. The process of accelerating the motor has been above described on the supposition that the contact segment 31 has been actuated to bridge the various contact members 30 gradually or all at once. ,It will now be shown that, if the radual operation is slow enough, it iS p0SSl le totobtain, in-

stead of a rapid acceleration of the motor,

a speed-control thereof. Assuming, then, that the controller handle has been actuated to its first position on the left, so that the contact segment 31 bridges the first two contact members 29, a circuitwill be established which will extend from bridged by the contact segment 31, the glimitswitch 35, the actuating coil of thereversing contactors 6 and 8, the conductor 4:6,

the safety lank switch 233, the emergency switch 33, t e limit-switches 35 and 34,

37, to the line conductor 1. The reversing contactors 6 and 8 are thereupon closed to establish the motor circuit foroperationinthe direction reverse to that established the. conductors 47, 201 and 101 and the switch when the reversing contactors 5 and 7 are closed. The motor circuit extends from the positive line -conductor 1, through the switch 37, the conductor 101, the reversing contactor 8, th e armaturefi, current now Howing intheopposite direction, the reversing .conta ctor 6,,the resistorQ, the contactor 39, the conductor43, and the switch 37, to the negative line conductor 2.

v The hrake ooilfill andthe coil; 54 are energized in thesame way as described above in connection with, the 1 motor circuit established upon .the-.o losing of the reversing switches 5 i-anddg the :oircuits beingras -follows: from, the line conductor 1, through the fSWit0hj37, the conductor 101, the reversing contactor fi, the :switch26, the coil'66, the; resistor- ;25,;the factuating, coil of :the relay- 23,,the conductors 1,65,; 265= and 365,- the brake. ;ooil;,53-, the conductor 153, :the'contalctor 3 9,.;th e conductor 43- :and the switch 37 ,rto;.;tl a;e :negative line conductor '2. For reasonsagiven-ialjoice, the coil of the relay 23, though energized; will not be sufiiciently energized- 1x1 Iilosefits-switch. @The circuit of the coil fi may heztraced; -as before,- item the conductor 165,2't'hrough the "conductor 6165, andthe;boil 54, to' the confiactor 39, and thencerto-the-line conductorr2.

glf the master-switch am he moved to its second, third-mud idomrth positions, results similar; those obtained :in connection "with the, previous -.--description will be obtained, in that-the coils of, the oontactors 1-10, 121 and 11;;will beenerg'ized, causing the closing of those switches and the opening of 'the switches 210,-!221and-59.- This will'he evident from thejact'th'at the third, fourth, fifth and sixth-contact members 29 are in parallel; relation: to the corresponding- 1 contact members 30. ;-If-,- however, the masterswitch' arm be maintained for a sufiiciently long period .of time in its first position, the contactors 110, 121;and. 11 iwillremain' open and the switches mechanically interlocked with them, viz: thosenumbered 210, 221 and 59' will remain closed; The motor will build up a.counter-electromotive force which will cause the energization of the coil 118 to cause-the closing ofithe contactor 18. This coil will remain energized so long as the switch 59 remains closed if the counter-electromotive force is sufiiciently great. The resistor 17 will thus be inserted into parallel circuit with the armature 3.

As there 'is not a great amount of current traversing .the circuit including the armature 3 andthe resistor'l'f, the actuating coil gized so long as the switch 221 is closed. The relay 219, closing immediately for the same reason which caused immediate closing of the relay 218, will cause the energize,- tion of the coil 120, the circuit of which contains the switch 210, to cause the immediate closing of the contactor 20. If, therefore, the master-switch arm be maintained in its first position, the resistor 17 will be connected in shunt to the armature 3 with two portions, viz: those controlled by the contactors 19 and 20, short-circuited, as indicated by dotted lines at Fig. 6. This results in giving to the motor a predetermined speed, which will be substantially uniform under varying loads because of the low-resistance shunt circuit through a section of the resistor 17.

If the master-switch arm now be actuated to its second position, so as to bridge the first three contact members 29 (or, if the master-switch arm be actuated to the right, the first three contact members 30), and the master-switch arm he maintained in that position, the actuating coil of the contactor 110 will be energized to cause the closing of this switch and the opening of the switch 210, which latter opens the circuit of thecoil 120, whereupon the contactor 20 opens to insert a second portion of the resistor 17 in parallel circuit with the armature 3030 long, there-- fore, as the master-switch arm is maintained in this second position, the motor will run at a second predetermined speed.

Actuation of the master-switch arm to its third position will cause the contact segment 31 to bridge the contact member 29 which controls the actuating: coil of the contactor 121. Upon the closing of this contactor, the switch 221 is opened and the actuating'coil 119 of the contactor 19 is deenergized cansing the opening of the contactor 19 and the consequent insertion into the armature circuit ofthe third portion of the resistor 17, as indicated'by full lines at Fig. 6; If the master-switch arm be not actuatedfurther', the resistor 17 will remain in parallel circnit with the armature 3 resulting in giving to the motor a third slow predetermined speed.

lVhen the master-switch arm is actuated to its fourth position, causing the energizetion of the actuating coil of the contactor 11 and the consequent closing of this contactor, the relay 59 will be opened to break the circuit of the coil' 118, thereby to cause the opening of the contactor 18 and the disconnecting of the resistor 17 from the motor circuit, as shown by full lines at Fig. 4. The closing of the contactor 11 permits the closing of the relay 58. This, in turn, causes the energizing of the actuating coil of the contactor 12, and, as before described, the contactors 12 to 16 close in succession to short circuit the resistor 9 and, after the resistor 22 has been inserted, following ac uation of the controller to its last position, to bring the motor up to full speed.

The decelerating operation is the same as before described in connection with the operation which obtains when the contact segment 31 is caused to bridge the contact members 30 and then return to ofi' position.

My counter-electromotive-force coil 118 plays a special function in connection with the usual limit switches 128 which are employed for stopping the motor at the bottom and top of the elevator shaft.

If the elevator car is approaching one of these limits of movement, with the motor operating under light load, the limit switches 128 willbe successively opened to break the circuits of the actuating coils of the contactors 11, 121 and 110 and the reversing contactors, so that the motor will be automatically slowed down and the car stopped at the desired limit of travel. The armature will be connected in a dynamicbrake circuit with the resistor 17, but this will not prevent the car reaching its limit of travel when the motor is operating with light load. Under heavy load, however, this dynamicbrake circuit may tend to stop the car before it'reaches the desired point of travel, in'which'case thelast limit switch 128 will not be opened to open the circuit of the reversing-contactor coil. When, however, the counter-electromotive force has become sufficiently reduced to permit the opening of the contactor 18, the master-switch arm being maintained in an operative position, the' motor will again accelerate slightly and the car be moved the remainin distance until the last limitswitch 128 has been opened to open the actuating coil of the reversing contactors. The carcannot now be restarted except in the reverse direction.

I thus provide [for stopping the car at substantially the same limiting points of travel under-any conditions of load, and whether the car is traveling up or down In accordance with the requirements of the patent statutes, I have described myinvention in connection with a motor-control system which I have chosen for purposes of illustration. It will be understood, however, that my invention is not restricted to the specific circuits and apparatus which are illustrated and described and that my in vention is to be construed broadly except in so far as limitations may be specifically imposed in the appended claims;

I claim as my invention:

1. The combination with an electric motor having an armature and a resistor, of means for connecting said resistor in parallel relation to said armature and means controlled automatically in accordance with the value eifective underpredetermined operating conof the current traversing said motor for diditions.

minishing the effective portion of said re- 9. The combination with an electric motor sister to effect the deceleration of said motor. having anflarmature, a switch operable in 2. The combination with an electric motor accordance with the value of the counterliaving. an armature and a resistor, of means electromotive force of said motor and a recontrolled by the counter-electromotive force sistor adapted to be connected in parallel reof said motor for inserting a portion of said lation thereto upon the closing of said switch,

resistor into parallel circuit with said arof means for effecting a speedy acceleration mature, and means controlled by the current of said moto without the aid of said retraversing said motor for inserting the resister and for effecting a slower acceleration maindcr of said resistor into parallel cirof said'motor with the aid of said resistor. cuit with said armature. 10. The combination with an electric mo- 3. The combination with an electric motor L01 having an armature, a resistor in series having an armature and resistors in series therewith andfia resistor adapted to be contherewith and in parallel thereto, of-a switch necte'd -in parallel thereto when the motor for controlling said seriesresi'stor, a-switch is moving at a predetermined speed, of for controlling said parallel resistor and means for reventing said connection during having an actuating coil adapted to be enerthe "normal accelerationof said motor, and gized by the counter-electromotive force means for efiecting said connection to conof said motor, and a switch mechanically trol the speedof said motor. connected to said first-named switch for '11. The combination with an electric momaintaining the circuit of said coil open tor having a resistor, of means controlled by when said first-named switch is .closedand the speed of said. motor for controlling the for closing the circuit of said coil when. said electrical connections-of said resistor, and first-named switch is open. 1 means comprising a master switch for ren- 4. The combination with an electric motor derin'g said controlling means ineffective having an armature, a resistor and a master when said switch is actuated above a predeswitch, of means for connecting said resistor termined rater i in parallel relation, to said armatur, and 12., The: combination with an electric momeans for varying the effective portion: of tor'h'avinga shunt field-magnet winding and said resistor in accordance with the position a resistor in circuit therewith, of a switch of said master'switch and the valueof the forrcontrolling said resistor, means controlled current traversing @315 motor. V by the speed of said motor for controlling 5. The combination with an electric motor, said switch, anda switch mechanically conof means operable at a predetermined speed nected to said controlling switch for renof said motor to establish a second andlower d'ering said controlling switch independent predetermined motor speed and operable, of said-,speed-donti'olled means. when the motor speed is, above a predeter? --1-3,-;'The' combination with an electric momined maximum rate, to openthe circuit of tor,- and aspeed-res ponsive device, of means said motor. I controlled'by-said-device-and operable under 6. The combiiiation3with an electric motor, emel ency conditions to decreasethe speed having a field-magnet winding, oi a speed.- ofsaid motor to a predeterminedmate, said responsive device for increasing the energimeans being operableito maintain said 1110- zation of said winding when the motor op: tor'a'tthe lower rate until themotor circuit crates above a predetermined speed and for is opened; opening the motor circuit when ,the motor 114. .The combination-with an electric moexceeds a second and higher predetermined torjand controller therefor operable through speed. i a predetermined cycle,- of a plurality of con- 7. The combination with an electric motor trol circuits for said motor, and means for having an armature, a resistor in parallel rendering one or another of said controlcin thereto, and a resistor in series therewith, cuits effective in accordance with the rate said series resistor being greater than is of theoperation of said -controller through necessary to start said motor on heav load, said; cycle. i of a time-element device for controlling said 15. The combination with an electric moparallel resistor and the excess portion of; tor, of speed-controlled means, operable said series resistor r; y when, the motor rotates above a predeter- 8. The combination with an-electric motor mined speed,- for; establishing a second and having an armature, a resistor and a master lower predetermined motor speed, and means Switch, of means controlled in accordance for maintaining the operation of said motor with the value of the counter electromotive at said second predetermined speed. force of said motor for connecting said re- 16. The combination with an electric mosistor in parallel relation to said armature, tor, of speed-contro1led means, operable when and means comprising said master switch the speed of said motor is abnormally high, for rendering said connecting means infor establishing a predetermined motor speed, and means for maintaining the operation of said motor at said predetermined speed until the opening of the circuit of said motor.

17. The combination with an electric motor and means for decelerating said motor, of means for automatically increasing the speed of said motor when said speed falls below a predetermined value.

18. The combination with an electric motor, of means comprising a resistor, a limit switch and a switch controlled by the counter-electromotive force of said motor and by said limit switch for automatically stopping said motor at a predetermined point in its operation.

19. The combination with an electric motor having an armature and a resistor in parallel relation thereto, of means controlled in accordance with the value of the counterele'ctromotive force of said motor for controlling the connection of said resistor to said armature.

20. The combination with an electric motor and means for effecting dynamic braking thereof, of a controlling switch, and means for rendering said dynamic braking means ineffective when the speed of said motor falls to a predetermined rate and said controlling switch is in an operative position.

In testimony whereof, I have hereunto subscribed my name this 29th day of N ov., 1918.

HAROLD L. KEITH. 

